The invention relates to the design of an ultra-low-friction rotating device for demonstration and amusement purposes. People have always been fascinated by the concept of perpetual motion which would imply motion continuing indefinitely without an external source of energy. Perpetual motion is impossible in practice since some form of friction is always present. To the extent that a body in motion will interact with other bodies or particles, friction will result. Celestial bodies can appear to achieve perpetual motion but are ultimately affected by interactions with particles.
According to Ernshaw's theorem, it is not possible to achieve stable levitation of a static magnet using other static magnets. However stable magnetic levitation is possible if diamagnets such as bismuth, graphite, or superconductors are used. Magnetic levitation may also be temporarily spin-stabilized without diamagnets as long as the levitating magnet is spinning at the proper rate. This approach has been popularized by the Levitron device which spins and precesses in air for a few minutes and continues indefinitely if air currents or magnetic pulses are used to supply energy.
Previously, ultra-low friction flywheels have been devised for energy storage which use magnets and superconductors in a high vacuum. High vacuum pumps and liquid nitrogen are continuously used and must be considered energy inputs. The magnetic bearing is typically spun up either with a gas stream feedthrough into the vacuum or with a magnetic motor attached to the same shaft. For viscous flow (low Reynolds number) high vacuum is needed because, until the mean free path of the gas molecules becomes comparable to the size of the rotor or rotor-stator gap, the viscosity and gas friction is independent of pressure. In practice, pressures below 10−2 torr are typically needed before friction drops linearly with pressure. One of the elements of the present invention is the use of vacuum tube technology which easily attains 10−6 torr without active pumping. When a half inch disk magnet is spun at atmospheric pressure, it has been found that spinning lasts approximately one hour. Assuming the drag is dominated by gas friction and this can be reduced linearly in the range between 10−2 and 10−6 torr, the magnet will spin for over 10,000 hours (more than one year) at this lower pressure. It is the purpose of this invention to simulate the near perpetual rotation of a celestial body due to weightlessness and high vacuum in a desktop device for demonstration and amusement purposes. It is also possible that the device can be used as a very sensitive torque or motion sensor.
Accordingly, there is need to create a device which levitates and spins an object for extended periods of time with a single, one-time energy input while additionally being low in cost.